1. S. Amarel, On representations of problems of reasoning about actions, in:Machine Intelligence, ed. Michie (Edinburgh University Press, 1986) chap. 10, pp. 131?171.
2. M.A. Arbib and E.G. Manes, Machines in a category: An expository introduction, SIAM Rev. 16, No. 2 (1974) 163?192.
3. R.B. Banerji and G.W. Ernst, A theory for the complete mechanization of a GPS-type problem solver, IJCAI-77 (1977) pp. 450?456.
4. D.P. Benjamin, L. Dorst, I. Mandhyan and M. Rosar, An introduction to the decomposition of task representations in autonomous systems, in:Change of Representation and Inductive Bias, ed. D. Paul Benjamin (Kluwer Academic Publ., 1990).
5. D.P. Benjamin, Reformulating path planning problems by task-preserving abstraction, J. Robotics and Autonomous Syst. 9 (1992) 1?9.